# Geometry/Chapter 13

Complementary angles are angles that the sum of their measures is equal to 90º.

File:Complementary angles|thumbnail|center </gallery> ]] Supplementary angles are angles that the sum of their measures is equal to 180º.

``` 90º              __|__               90º
_________________|__|__|____________________
```

## Vertical Angles

In the above diagram, A and C are vertical angles, and B and D are vertical angles. Vertical angles are congruent.